1. Field of the Invention
The present invention relates generally to tactical firearms that are utilized by tactical and special operations personnel for military and law enforcement activities, particularly cartridge gas operated firearms such as the military M-16 and the commercial AR-15. More particularly, the present invention concerns a firearm barrel assembly having multiple, i.e., two or more, gas ports in communication with the bore of the barrel, with at least one of the ports being controlled by a selector valve for selecting open and closed port valve positions. The port selector valve controllable multiple port gas system of the barrel permits reliable firearm operation to occur normally and when gas pressure changing devices such as suppressors are in gas receiving and bullet transmitting assembly with the firearm barrel.
2. Description of The Prior Art
To the knowledge of applicant most AR-15 and M-16 autoloading firearms incorporate a barrel to which various types of flash and noise suppressors may be attached. The barrel is provided with a gas block that is mounted to the barrel and has an internal gas passage that is in communication with a single gas port which is formed in the barrel and communicates with the barrel bore.
In the event of change of cartridge gas pressure or volume that enters the gas tube from the gas passage of the gas block and the port of the barrel it is possible for the firearm to fail to function properly. This condition is evidenced by failure of proper cartridge loading, cartridge hang-ups in the breach, failure to retrieve a cartridge from the magazine of the firearm, etc.
When a compensator or suppressor is attached to the forward end of a rifle barrel the result is a change of cartridge gas pressure conditions within the barrel bore and also a change of the timing sequence for cartridge gas pressure rearward actuation of the piston rod and the bolt that is actuated rearwardly by the piston rod. Thus, when a compensator or suppressor is attached to the barrel, the barrel bore pressure is lowered, thus causing a delay in piston movement and slower piston movement by the cartridge gas pressure. The bolt within the receiver is thus moved more slowly by the piston energized actuator rod so that the bolt may not be moved completely to the cartridge case ejecting position against the force of the bolt return spring. A cartridge case may be extracted from the cartridge chamber of the barrel and may be partially, but not completely ejected by the rearwardly moving bolt and may interfere with the subsequent spring energized forward bolt movement or a released cartridge case may interfere with the cartridge loading and bolt closing process of a firing cycle, thus potentially causing the cartridge handling mechanism to jam. When a jamming condition has occurred it is necessary to manually move the bolt rearwardly to eliminate the cartridge case jam and to ensure that a subsequent live cartridge is moved by the bolt from the cartridge magazine into the cartridge chamber of the barrel.
It is desirable therefore to provide for selective change of cartridge gas pressure or volume to the gas tube of the firearm to thus restore proper operation of the firearm in the event the use of a larger suppressor should cause improper firearm operation.